Dr. 0. Davison on Earthquake-Sounds. 33 



to a vehicle driven quickly past, to illustrate apparently the 

 evenness of the sound or the rapidity with which it attains 

 and recedes from its maximum intensity. The common illu- 

 sion that an underground train rushes up to and beneath a 

 house, and continues its journey in the opposite direction, is 

 no doubt due to this gradual rise and fall in intensity. 



Types of Earthquake- Sound. 



A few observers find it difficult to describe the sound, but 

 most compare it to some well-known type, and the resemblance 

 in many cases is so close that the observer at first attributed 

 it to the object of comparison. The descriptions which I 

 have examined, several thousands in number, may be classified 

 under the following heads : — 



(1) Waggons fyc. jiassing. — One or several traction-engines, 

 either alone or heavily laden, sometimes driven furiously past ; 

 a steam-roller travelling at a quicker pace than usual or 

 passing over frozen ground ; heavy waggons coming quickly 

 down a hill, driven over stone paving, on a hard or frosty 

 road, in a covered way or narrow street, or over hollow 

 ground or a bridge ; a heavy roller on a garden path, or a 

 wheelbarrow on a hard and frosty road ; express or heavy 

 goods trains rushing through a tunnel or a deep cutting, 

 crossing a wooden bridge or iron viaduct, or a heavy train 

 running on snow ; also, the dragging of heavy furniture or 

 boxes across an adjoining floor, the grating of a boat on a 

 beach or of the bottom of a large vessel when dragged over 

 rocks. 



(2) Thunder. — A loud clap or heavy peal, sometimes dull, 

 hollow, muffled, or subdued, but most often distant, and thus 

 conveying the impression of a low deep booming sound. 



(3) Wind. — A moaning, roaring, howling, rushing, hissing, 

 or rough, strong wind ; the rising of the wind, the roaring of 

 a great squall, a heavy wind pressing against the house, or a 

 high wind sweeping through trees ; the howling of wind in a 

 chimney, a chimney on fire, and the blare of a furnace when 

 the door is opened. 



(4) Loads of stones Sfc. falling. — The tipping of a load of 

 coal, stones, or bricks ; a wall or roof falling, or the crash of 

 a chimney through the roof. 



(5) Fall of heavy bodies. — The fall of a heavy weight, of a 

 tree or heavy timber ; the thud of a large mass of snow from 

 a house-top, the banging of a door, only more muffled, and 

 the blow of a wave on the sea-shore. 



(6) Explosions. — The explosion of a boiler, a cartridge of 

 Phil Mag. S. 5, Vol. 49, No. 296. Jan. 1900. D 



